A Zebra Among Zebras

A 52 year-old woman with hypertension, insulin dependent type II diabetes, mild non-proliferative diabetic retinopathy in both eyes, obstructive sleep apnea, paroxysmal atrial fibrillation, obesity and multifactorial end-stage renal disease (ESRD) complained of four days of a dark scotoma in the inferior portion of the right eye that began right after hemodialysis. The scotoma migrated inferiorly and enlarged over four days. One month prior to presentation she developed intermittent jaw pain on chewing, worse on the right side. On ophthalmic examination, visual acuity was count fingers at three feet for the right eye and 20/60 with pinhole improvement to 20/25 in the left eye. There was a 2+ relative afferent pupillary defect (RAPD) in the right eye. The anterior segment examination was notable only for bilateral mild nuclear sclerosis. Fundus examination of the right eye showed 360° optic disc edema with chalky temporal pallor and a flame hemorrhage superior to the disc. The left optic disc was without edema or pallor with a 0.2 cup to disc ratio. In light of the presence of jaw claudication and pallid edema, an arteritic anterior ischemic optic neuropathy (AION) due to giant cell arteritis (GCA) was suspected. Fluorescence angiogram demonstrated leakage of the right optic disc with normal retinal and choroidal filling. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were elevated to 90 mm/hr and 4.3 mg/dL, respectively, but platelet count was normal at 229 per uL. Brain MRI revealed several punctate acute infarcts across several vascular territories including the bilateral high frontal and; left occipital white matter, as well as a punctate focus of restricted diffuse at the insertion of the right optic nerve head. Neck MRA showed no significant stenosis. Head MRA showed no signs of inflammation in the temporal artery walls.